1. Field of the Invention
The present general inventive concept relates to a method and system to detect orientations of a moving object using magnetic compasses, and, more particularly, to a method and system to minimize magnetic field interference in a space in which an object is moving such that the orientations of the moving object can be precisely detected.
2. Description of the Related Art
Generally, robots have been used for various purposes in various industrial fields. For example, moving robots (hereinafter, referred to as moving objects) that have been used indoors, such as cleaning robots, service robots, etc., must detect their orientation so that their movement may be precisely controlled.
One type of sensor for detecting the orientations of the moving object is a magnetic compass which calculates an azimuth of the moving object i.e., an absolute orientation using a direction of the Earth's magnetic field (EMF), which is always oriented toward the north pole.
A method of detecting orientations of a moving object using a magnetic compass was proposed by L. Ojeda and J. Borenstein in Proc. Of IASTED Int. Conf. Robotics and Applications, Honolulu, Hi., 2000 entitled “Experimental results with the KVH C-100 Fluxgate Compass in Mobile Robots.”
As illustrated in FIGS. 1 and 2, the method disclosed in the abovementioned document reads two azimuths θc1, θc2 from two magnetic compasses 3 installed on a moving object 1 in step S10, and compares the two azimuths θc1, θc2 with one another in step S11. If the two azimuths θc1, θc2 are equal to each other, a determination is made that there is no magnetic field interference in the space where the moving object is located, and accordingly, one of the two azimuths, i.e., θc1, is set as an orientation θ of the moving object 1 in step S12. Otherwise, step S10 is repeated to perform the azimuth determination procedure.
However, as illustrated in FIG. 3, since there is an area where a magnetic field interference is present, within the indoor space in which the object 1 is moving, outside of an Earth's magnetic field (EMF) area, the magnetic compasses 3 cannot direct the moving object 1 north in the area of the magnetic field interference. Namely, the magnetic field interference causes interference with a determination of the earth's magnetic field in the magnetic field interference area.
In such a situation, if the two magnetic compasses 3 have the same value, a determination is made that no magnetic field interference occurs in that area, thereby causing fatal errors when determining the orientation of the moving object 1.
On the other hand, there are cases when the two magnetic compasses 3 have the same value as a result of the magnetic field interference in the magnetic field interference area. Since the value may be quite different from an azimuth of the EMF, the method of detecting the orientation of the moving object of FIG. 2 has disadvantages in that it cannot determine whether the azimuth acquired from the magnetic compasses 3 is an azimuth of the EMF or an azimuth that results from magnetic field interference.